A soppy pet? (5,3)

I believe the answer is:

water dog

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'a soppy pet?' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'soppy pet?' is the wordplay.
'soppy' becomes 'water' (I am not sure about this - if you are sure you should believe this answer much more).
'pet?' becomes 'dog'.
'water'+'dog'='WATER-DOG'

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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